1. Field of the Invention
The present invention relates to a wind driven electrical power generating apparatus for driving a generator by rotating a rotor utilizing wind force. Particularly, the present invention relates to a wind driven electrical power generating apparatus for controlling a gear assembly, which connects a rotor and a generator, so that the apparatus operates for a long period of time and at the same time, at optimal power-conversion efficiency. Furthermore, this invention relates to an improvement of a gear assembly employed in a wind driven electrical power generating apparatus and interposed between a rotor and a generator so as to decrease or increase an input rotational speed.
2. Description of the Related Art
A wind driven electrical power generating apparatus utilizing wind force converts the kinetic energy of wind to drive force by using a rotor such as propeller-type rotor and the like, which rotates by receiving the wind force, and then drives a generator by using the drive force, resulting in the conversion of the wind force to electrical energy. As is seen in the above-described mechanism of the wind power conversion process, the wind driven electrical power generating apparatus fundamentally depends on wind, one of natural phenomena, and therefore, the output electrical energy of the apparatus drastically fluctuates depending on the natural condition of not only the day but also the time. When wind speed varies, the rotational speed of a rotor also varies in accordance with the change of the wind speed, leading to the change of the rotational speed of a generator, and finally resulting in the fluctuation of the electrical energy to be generated.
Conventionally, there have been proposed various techniques to improve a wind driven electrical power generating apparatus. Among those techniques, Japanese Patent Laid-Open Publication No. Hei. 2-157483 discloses the following technique. That is, a gear assembly is interposed between a rotor and a generator such that the input shaft of the gear assembly is connected to the rotor and the output shaft of the gear assembly is connected to the rotating shaft of the generator, and by adjusting the gear ratio of this gear assembly, the rotational speed of the output shaft is controlled to be within a predetermined range of rotational speed regardless of the rotational speed change of the rotor. In addition, Japanese Patent Laid-Open Publication No. Sho. 62-129578 discloses the following technique. That is, the pitch of rotor blades is made to be variable and can be controlled in accordance with wind speed so as to always rotate a generator within a predetermined range of rotational speed.
It is an object of the present invention to provide a wind driven electrical power generating apparatus capable of operating at optimal power-conversion efficiency and elongating the life of the power generating apparatus.
According to one aspect of the invention, a wind driven electrical power generating apparatus includes a rotor rotating by receiving wind force, a gear assembly connected via an input shaft thereof to the rotor, a generator connected to an output shaft of the gear assembly, a sensor for detecting a generating capacity of the generator, and a controller for varying a gear ratio of the gear assembly in accordance with a signal from the sensor to control the generator to keep rotating at around the lowest rotational speed within a range of rotational speed, the range being determined so as to include a maximum power operation region of the generator.
According to another aspect of the invention, a wind driven electrical power generating apparatus includes a rotor rotating by receiving wind force, a gear assembly connected via an input shaft thereof to the rotor, a generator connected to an output shaft of the gear assembly, a sensor for detecting parameters representing an output power of the generator, and a controller for varying a gear ratio of the gear assembly in accordance with a signal from the sensor to control the output shaft of the gear assembly to rotate at around a lowest rotational speed within a range of rotational speed, the range being determined so as to include a rated power region as an upper operational limit.
That is, by controlling the gear ratio of the gear assembly for the generator to operate within a range of power limited to its rated power as an upper operational limit, the generator becomes capable of generating its maximum electrical power and at the same time, can be prevented from rotating at a higher rotational speed than required for outputting its maximum power, whereby the life of the generator is elongated. Note that an operational limit on usage of a generator under specified conditions is referred to as rating and usually represented by output power referred to as rated power. In other words, the rated power of generator means maximum generating capacity of the generator under operation. Parameters featuring the output power of generator include rotational speed, current, voltage, electrical power and the like. Therefore, to the sensor of the apparatus can be applied a sensor suitable for the parameter to be detected.
The wind driven electrical power generating apparatus of the present invention has the following configuration. That is, the rotor and the generator are connected to each other via the gear assembly, and the controller for varying the gear ratio of the gear assembly based on a detected signal from the sensor, which detects parameters representing the output power of the generator, is provided. The controller adjusts the output shaft of the gear assembly to rotate at around the lowest rotational speed within a range of rotational speed, the range including a rated power region as an upper operational limit. Therefore, the generator of the apparatus is capable of always outputting the electrical power approximately equal to the rated power at optimal efficiency and at the same time, the rotational speed of the generator is limited to around a lowest rotational speed needed for the generator to output the above-described electrical power, whereby the life of the generator is elongated.
Various known types of gear assemblies can be employed as the gear assembly of the present invention. For example, a belt pulley type gear assembly, a planetary toothed-wheel type gear assembly and a traction drive type transmission can be available. Furthermore, the gear assembly to be employed in the apparatus is not necessarily to be a continuously variable gear assembly but may be a multi-stage gear assembly.
According to still another aspect of the present invention, a gear assembly for a wind driven electrical power generating apparatus includes:
a casing;
an input shaft rotatably supported in the casing;
an output shaft rotatably supported in the casing;
a sun roller rotating with the output shaft;
an outer ring disposed coaxially with the sun roller; and
a plurality of kinds of roller groups disposed in a radial direction in a space formed between the sun roller and the outer ring, and being frictionally engaged with the sun roller and the outer ring,
in which each of the roller groups is rotatably disposed at equal intervals in a circumferential direction, the roller groups are disposed being stacked one above another in a radial direction in a multi-stage fashion, and each roller belonging to at least one roller group selected from the roller groups has rollers constructed of a plurality of cylinders to have two raceway surfaces having different rotational radiuses. According to the above-described configuration of the gear assembly, all the roller groups are arranged within the same plane. Therefore, compared with the above-mentioned conventional gear assembly configuration in which two gear assemblies are disposed in series in an axial direction, the gear assembly of the present invention can achieve the gear ratio equivalent to that of the two gear assemblies in such a compact and space saving manner as smaller dimension in an axial direction. Furthermore, the outer ring may be integrally formed as one-piece structure with the casing. Thus, the number of parts needed for gear assembly can be reduced and further reduction of dimension of gear assembly in a radial direction can be achieved. According to the present invention, in addition to the achievement of high gear ratio, a lightweight and compact wind driven electrical power generating apparatus can be provided. That is, all the roller groups are arranged within the same plane. Therefore, compared with the above-mentioned conventional gear assembly configuration in which two gear assemblies are disposed in series in an axial direction, the gear assembly of the present invention can achieve the gear ratio equivalent to that of the two gear assemblies in such a compact and space saving manner as smaller dimension in an axial direction.
In this construction, the gear assembly may be configured in such a manner that the outer ring rotates with the input shaft and each roller belonging to the roller group being frictionally engaged with the outer ring is rotatably supported on a pin fixed to the casing.
Furthermore, the gear assembly may be configured in such a manner that the outer ring is made not to rotate, and each roller belonging to the roller group being frictionally engaged with the outer ring is rotatably mounted on a carrier provided on the input shaft.
Furthermore, the gear assembly may be configured in such a manner that the outer ring is made not to rotate, and the input shaft and each roller belonging to the roller group being frictionally engaged with the outer ring constitute a toothed-wheel transmission mechanism. Although the traction drive is featured by low vibration and low noise, it utilizes rolling and sliding contact mechanism and therefore, the transmissibility is inferior compared to that of a toothed-wheel transmission mechanism. Since the rotational speed of an input side (a rotor side) is low, even when the traction drive is replaced by the toothed-wheel in the apparatus, vibration and noise do not become so serious problems. Taking into account of such features seen in the two mechanisms, the gear assembly is made to be configured so that the input side rotating at a low speed employs a toothed-wheel and the output side needed to rotate in a high speed employs a traction drive, and thus, the power transmissibility of gear assembly is improved and the power received from the rotor can be transmitted to the generator without loss. The above-stated effect is achieved even in the modified conventional technique. That is, out of the two-stage planetary rollers disposed in series in an axial direction in the gear assembly described in Japanese Patent Laid-Open Publication No. Hei. 5-79450, the input side (the rotor side) planetary rollers are replaced by planetary toothed-wheels. However, according to the present invention, a gear assembly having the same effect as that of the modified conventional technique can be realized in an axial direction dimension in a more compact manner than the gear assembly configured to be arranged in two-stage in series in an axial direction.
Furthermore, the gear assembly and the generator may be made to be of one-piece structure. For example, the sun roller can be directly connected to the rotating shaft of the generator. Thus, the output shaft can be omitted and at the same time, the bearing for supporting the output shaft also can be omitted. Furthermore, a part of the casing of the gear assembly can be configured to be commonly formed with the generator casing, thereby realizing the wind driven electrical power generating apparatus wholly in a space saving manner.
Hereinafter, preferred embodiments of the present invention will be explained with reference to the drawings.